Magneto construction



April 17, 1934. w E R N 1,954,828 7 'MAGNETO CONSTRUCTION:

Filed Nov. 9, 1952 I N V EN TOR. [WW0 14/ PETFRS 5 v ATTORNEY.

Patented Apr. 17, 1934 UNITED STATES PATENT OFFICE 1,954,828 MAGNETO CONSTRUCTION Eyvind W. Petersen, Beloit, Wis., assignor to Fairbanks, Morse & 00., Chicago, Ill., a corporation of Illinois This invention relates to improvements in magneto constructions, and more particularly to improvements in methods of forming magnetos of the inductor type.

In certain prior magneto constructions of the inductor type, it is usual toemploy screws or other like fastening means for securing the laminated pole shoes and the permanent magnets,-

usually of the horseshoe type, to the frame structure of the magneto. Such constructions are objectionable in that the screws or other like fastening means often become loose and ineffective. In magnetos of this-type it is desirable to employ permanent magnets formed of a cobalt steel or other similar material having high magnetic retentivity. Such materials have not been widely used in magnetos of this type because of the difliculty experienced in machining the permanent magnets, and in securing them to the frame elements of the assembly.

An object of the present invention is to provide an improved pole piece holding structure for magnetos of the inductor type, which includes a mass of die-cast non-magnetic metal for uniting, into an integral structure, the laminated pole shoes and magnetic pole piece bridging members, and which serves as a frame structure for positioning the pole pieces or permanent magnets.

A further object is to provide an improved inductor type magneto in which the laminated pole shoes'and the magnetic bridging members are intimately united into a unitary structure by means of a mass of die-cast, non-magnetic metal, and in which the pole pieces are assembled and more firmly secured to the die cast mass, than is possible through the use of screws, bolts, nuts or the like.

A still further object is to provide an improved inductor type of magneto, which is rigid' and durable in construction, and is composed of but a few simple -and'readily assembled parts, and which results in a'. substantial reduction of production andassembly costs, through minimization of assembly operations. as well as machining operations on the permanent magnets.

Still further objects and advantages will appear from the following detailed description of parts and from the accompanying drawing of a preferred embodiment of the invention, and in which: 7 V

Fig. 1 is a longitudinal sectional elevation, taken along staggered planes, as indicated by the line 11 of Fig. 2; Fig. 2 is a transverse sectional elevation of the structure of Fig. 1, and as indi shaft 12.

chining operations.

cated by line 2-2 of Fig. 1, and Fig. 3 is a transverse sectional elevation along line 3-3 of Fig. 1.

Referring to the drawing by reference characters, the numeral 10 designates. generally. a preferred form of magneto of the inductor type. and which includes. by preference. a laminated inductor structure 11 suitably secured to a rotor This inductor structure consists. by preference, of stacks of soft iron laminations, each of partly fan shape, which are secured together by suitable means (not shown) and secured, as 'by a key, to the rotor shaft. This shaft and rotor structure is, by preference, suitably journalled in bearings, which are not shown in detail, being omitted for clearness. The inductor is mounted to rotate between the faces of laminated pole shoes 13, each of which consists of a stack or soft iron laminations. The individual laminations are of somewhat elongate form, and each provided, by preference. with a pair of pole-receiving apertures 14. The laminations constituting the pole shoes are also laterally recessed, the recesses, in assembly, forming a concave pole face adjacent the periphery so of the rotor. A plurality of pole pieces or permanent magnets 15 are arranged in spaced relation and substantially parallel to each other, and to the longitudinal axis of the rotor shaft 12. These pole pieces are, by preference, formed of cobalt steel or other material possessing high magnetic retentivity. and are formed, by preference, of circular cross section, to facilitate ma- In the example selected for illustration the magneto includes four such pole 00 pieces. although it will be understood that the number may be varied, depending upon the type and number of poles of the magneto to be con structed.

A pair of pole-bridging members 16, of soft iron or steel, are disposed near one end of the magneto I frame. each in contact with the end face portions site polarity. to provide a structure which is, in

effect. a U-shaped permanent magnet. By this arrangement there are provided two distinct magnetic circuits within a two pole machine. such as illustrated.

In assembling the machine, the laminated pole shoes, together with the bridging members 16, are suitably positioned, in the relation of their final assembly, in a die casting mold. The mold, prior to casting, is provided with cores corresponding in size and shape with, and so as to result in, pole-piece-receiving bores or passages 17, a core being also provided to form a central bore or passage to receive the shaft and inductor. A mass of non-magnetic metal 18, such as a suitable aluminum and/or zinc alloy, is then poured into the mold, preferably under pressure, for intimately uniting into a unitary structure, the assembled laminations constituting the pole shoes and the bridging members. This mass of metal, as shown, thus constitutes not only a frame structure for the machine, but also a holder for the polepieces. After the die casting process, the resulting rigid, integral structure is removed from the mold, the cores corresponding to and forming the passages 17, as well as the central bore, are removed from the casting, and the pole pieces 15 are inserted in and pressed to final position through the pole shoe apertures 14, and the cored passages 17, being urged into intimate contact with the soft iron bridging member 16, to insure a good magnetic path between the bridging members and the pole pieces.

Following insertion of the pole pieces 15, an end plate 19 is utilized, after assembly of the shaft and inductor, as a closure for one end of the corresponding plate portion 20, at the osite end of the frame, is conveniently formed a part of the cast body 18. If desired, the portions 19 and 26 may serve as bearing arms, to receive shaft bearings of suitable type. The frame structure or body of the magneto is completely assembled at stage, and it will be apparent that, by above arrangement and casting expedient, all screws or other iike fastening means for assembling the frame, are eliminated, being replaced by the much easier and more secure assembly expedient provided by the mass of cast metal.

Each pole shoe lamination is, by preference, provided with a portion 21 projecting laterally of the body of cast metal, the ends of the arms 21 being bridged by a steel bar 22 which forms the core of a coil 23, which may consist of a single or double winding, according to the type and intended use of the magneto. The bar 22 is conveniently secured to the ends of the pole shoes, as by machine screws, extending into tapped openings in the end faces of the shoes. It will be apparent that, after assembling the inductor structure 11,

and the end plate 19, the machine is completely assembled, and ready for use upon being provided with the requisite condensers, breaker assemblies etc.,'forming no part of the present invention.

In the construction above described, it will be seen that the cast mass of non-magnetic metal secures the various parts of the magneto into a unitary frame structure, and that the inductor structure'll, carried on the rotor shaft, is the only major movable element in the device. Such an assembly is neat and compact in construction, and forms practically a rigid, solid frame or polepiece holding structure, making for economy in material, and a reduction in production and assembly costs.

It will, of course, be understood that the present detailed description of parts and the accompanying drawing relate to only a single preferred executional embodiment of the invention, and that substantial changes may be made in the described method of construction and arrangeesass ment of parts, without departing from the spirit and full intended scope of the invention.

I claim:

1. An inductor type magneto including spaced parallel pole pieces, a member endwise abutting and magnetically bridging certain of the pole pieces, pole shoes extended across certain of the pole pieces, and therebeyond to form a winding support, a body of pressure cast metal embracing the bridging member, and provided with cored passages of a sectional shape and area to receive the pole pieces with a press fit, and of a length to embrace the pole pieces over at least a portion of their length, said metal body being provided with a preformed passage or bore centrally and longitudinally thereof, shaft mounted to operate in said bore and a rotor carried by said shaft and arranged to operate between said pole shoes.

2. In a magneto, a frame structure including a plurality of pole pieces arranged in angularly spaced relation about the frame, pole shoes extending substantially across opposite sides of the frame, and beyond the frame to form a winding support, a body of non-magnetic cast metal, embracing the pole shoes and pcrti ns of the pole pieces, and adapted to maintain the pole pieces and shoes in assembled relation, said cast body having a central shaft-rotor receiving passage,

and a plate member cast within the body and magnetically bridging a plurality of said pole pieces.

3. A hollow frame for pressure-cast non-ferrous of an open end structure pr ed with parallel longitudinal cored passage including a shaftand rotor-receiving passage centrally of the structure and magnet-receiving passages peripherally of the structure, and a magnet-bridging plate of ferrous metal disposed transversely of and within the cast body in bridging relation to a plurality of said magnet-receiving passages,- the magnet passages being of a size and section to receive and position the magnets with a driving fit.

4. In a magneto, a shaft, a. rotor carried by said shaft, a plurality of pole pieces disposed parallel to and spaced about the shaft and rotor, a plate element abutting and bridging end face portions of a pluralityof said pole pieces, pole shoes disposed adjacent the path of said rotor, and a body of cast metal, substantially embracing the bridging element, and portions of the pole shoes, and provided with cored passages of a size and shape to provide a driving fit therein, of the pole pieces.

5. In a field frame for a magneto, a plurality of pole pieces carried in parallel relation longitudinally of the frame, a plate bridging the end faces of a pair of said pole pieces near one end of the frame, laminated pole shoes interconnecting certain of the pole pieces, near the opposite end of the frame, the pole shoes being extended to form a winding support beyond the frame,

formed. of tal. and consisting and a mass of cast, non-magnetic metal, provided with cored passages tightly embracing the magnets, and surrounding the laminations constituting said pole shoes, and the bridging memher.

6. A frame structure for a magneto, including spaced parallel pole pieces disposed longitudinally of the magneto axis, a plate member magnetically bridging certain of the pole pieces, pole shoes arranged in bridging relation across the end faces of certain of the polepieces, and a body of cast pole-piece-bridging members magnetically inter connecting pole pieces of opposite polarity, a pair of pole shoes, one disposed at each side of the frame, each of said shoes being of laminated construction, apertured to form passages therethrough for the pole pieces, and extending laterally of one side of the frame, a body of diecast non-ferrous metal surrounding the several pole pieces and the bridging members, and embracing the pole shoes, said die-cast body having a longitudinal axial passage therethrough adapted to receive a shaft, an inductor type rotor carried by said shaft and disposed within said passages between the pole shoes, the laterally extended portions of the pole shoes constituting a support for an external winding, a bar of ferrous metal bridging the ends of the pole shoe extensions, and a winding carried by said bar.

EYVIND W. PE'I'ERSEN. 

